The present invention relates to active optical devices and, more particularly, to an optical chip device that can be connected on its back side and edges to provide new and unusual, high precision, chip level, interconnect configurations.
Active optical devices, such as VCSELS, edge emitting chips, receiver chips, transmitter chips, etc., having active optical elements, such as lasers, light emitting diodes, light receiving diodes and photo transistors, are usually mounted and connected on a single side to a substrate. They are commonly mounted with a two-dimensional orientation. Only a small vertical component is generally present, using several attachment methods including flex circuit, wire bond and so-called C4 technologies.
Conventional chip-to-optical device attachment techniques are often labor-intensive and prone to inaccuracies. This is due in large part to the extremely small dimensions of the components and their interfaces, as well as to the number of manufacturing and assembly steps required to interconnect those components.
The present invention reflects new optical chip interconnect configurations, wherein all six faces of the chip can be used to interconnect the back side and edges of the optical chip, using standard semiconductor optical lithography and metallization processes and a new, simplified assembly technique.
In U.S. Pat. No. 5,857,049, issued on Jan. 5, 1999, to Beranek et al, for PRECISION ALIGNMENT OF OPTOELECTRONIC DEVICES, an optoelectronic module is shown that is precisely aligned with an optical fiber. The module is solder connected to the optical fiber supported upon a base, and surface tension of molten solder is used to self-align the connection of the components.
In U.S. Pat. No. 5,818,107, issued to Pierson et al, on Oct. 6, 1998, for CHIP STACKING BY EDGE METALLIZATION, an integrated circuit package is illustrated, wherein increased mechanical and electrical reliability are achieved by integrated circuit chips formed into a chip stack, and bonded onto a substrate. The thickness of a metallization feature and the bonding material provide a stand-off between chips that allows improved heat dissipation.
In U.S. Pat. No. 5,790,730, issued to Kravitz et al, on Aug. 4, 1998, for PACKAGE FOR INTEGRATED OPTIC CIRCUIT AND METHOD, a structure and method are shown for packaging an integrated optic circuit having multiple microlenses. Surface grating forms channels between the optical circuit and the microlenses. Alignment for registration patterns is achieved using surface tension of molten solder in a plurality of solder bump bonds.
In U.S. Pat. No. 5,687,267, issued to Uchida on Nov. 11, 1997, for INTEGRATED OPTOELECTRONIC COUPLING AND CONNECTOR, an optoelectronic module is optically aligned with optical fibers on a common substrate having V-shaped alignment grooves.
In U.S. Pat. No. 5,675,889, issued on Oct. 14, 1997, to Acocella et al, for SOLDER BALL CONNECTIONS AND ASSEMBLY PROCESS, two substrates are aligned and connected using the surface tension of molten solder.
In U.S. Pat. No. 5,661,831, issued to Sasaki et al, on Aug. 26, 1997, for OPTICAL MODULE HAVING SELF-ALIGNED OPTICAL ELEMENT AND OPTICAL WAVE-GUIDE BY MEANS OF BUMPS ON RECTANGULAR PADS AND METHOD OF ASSEMBLING THEREOF, an optical module is shown mounted, with a wave guide and a laser diode, upon a silicon substrate. Surface tension of molten solder is used to self-align the laser diode array to a patterned pad on the silicon substrate.
In U.S. Pat. No. 5,631,988, issued on May 20, 1997, to Swirhun et al, for PARALLEL OPTICAL INTERCONNECT, optical fibers are interconnected to an array of optical devices, and aligned by surface tension of melted solder joining the two elements. Alignment holes are laser drilled in a substrate. Pads are formed through lithography relative to the holes. Then flip-chip technology is used to align the chip to the pads laterally.
In U.S. Pat. No. 5,337,398, issued to Benzoni et al, on Aug. 9, 1994, for SINGLE IN-LINE OPTICAL PACKAGE, an optical packaging arrangement is shown. Solder bump alignment is used to align the active device, the lens, and the lens holder. A fiber ferrule is placed over the assembled components with a modicum of precision.
In U.S. Pat. No. 5,535,296, issued on Jul. 9, 1996, to Uchida, for INTEGRATED OPTOELECTRONIC COUPLING AND CONNECTOR, an integrated mounting assembly is illustrated, wherein optical fibers are supported between a grooved substrate and a clamping substrate. The optical fibers are coupled to a device. Alignment is achieved by surface tension of melted solder.
In U.S. Pat. No. 5,499,312, issued to Hahn et al, on Mar. 12, 1996, for PASSIVE ALIGNMENT AND PACKAGING OF OPTOELECTRONIC COMPONENTS TO OPTICAL WAVEGUIDES USING FLIP-CHIP BONDING TECHNOLOGY, a method and apparatus are shown for automatic alignment of optical waveguides to photonic devices. Wettable pads are used and surface tension helps align the elements.
In U.S. Pat. No. 5,420,954, issued on May 30, 1995, to Swirhun et al, for PARALLEL OPTICAL INTERCONNECT, optical fibers are interconnected to an array of optical devices, and aligned by surface tension of melted solder joining the two elements.
In U.S. Pat. No. 5,247,597, issued to Blacha et al, on Sep. 21, 1993, for OPTICAL FIBER ALIGNMENT, an optical fiber is aligned with an emitting or receiving surface, using surface tension of solder bonds.
In U.S. Pat. No. 5,197,609, issued on Jan. 12, 1993, to Blonder et al, for OPTICAL ASSEMBLY INCLUDING FIBER ATTACHMENT, surface tension of liquified materials is used to face-align fibers disposed in a groove, with an optical device.
In accordance with the present invention, there are provided an optical packaging structure and method for producing same. The structure comprises a substrate having electrical contact pads and alignment pads with precision aligned through-holes for at least one optical fiber. The optical fiber(s) are supported by a housing, or coupler, having alignment pins that are precision located relative to the through-holes in the substrate and the optical fiber. A die, having at least one active optical element on a first die surface and electrical contacts on a second die surface, is aligned with the electrical pads of the substrate and the active optical element(s). The electrical contact pads are conductively bonded to the electrical contacts on the second die surface. The alignment pins are bonded to the precision aligned through-holes in the substrate.
The method incorporates the steps of grinding pins and optical fiber(s) in one pass and then aligning the active optical device and the optical fibers by surface tension of solder or other conductive adhesive liquid. The substrate comprises copper circuit contacts and doughnut shaped alignment pads that are used as an etch mask to allow removal (hole formation) of substrate material in a central region of the alignment pad. This precision aligned hole, which aligns with the electrical contacts of the substrate, is used to align the optical fibers in the housing, using pins. Solder balls connect the die to the substrate and the adhesive; or solder on the doughnut pads fix the optical fibers to the substrate.
It is an object of this invention to provide an optical chip device that can be connected on its back side and edges to provide new and unusual, high precision, chip level, interconnect configurations.
It is another object of the invention to provide an optical chip package for coupling a fiber optic cable to a transmitting die.